Human rights groups have condemned the execution by the Hamas government in Gaza of three prisoners at the weekend, and are demanding that the death sentence of a fourth be commuted.

The three men, identified only by their initials, were hanged on Saturday at a Hamas security base in Gaza City. The cases were unrelated: WJ, 27, had been convicted of treason by collaborating with Israel; MB, 49, had been convicted of murder; and MA, 20, had been convicted of abducting, raping and killing a child.

All three had exhausted the right to appeal, according to the interior ministry in Gaza. The victims' families refused to forgive the men or accept compensation in lieu of their executions, which were aimed at "protecting the safety of the public", the interior ministry said in a statement.

The execution of a fourth prisoner, Jamil Zakaria Juha, 29, who was sentenced to death by firing squad in December for complicity in murder, is expected imminently. The supreme military court in Gaza upheld Juha's sentence in February and he has no further appeals.

Since Hamas took control of Gaza in June 2007, after an electoral victory and a bloody power struggle with its political rivals Fatah, the government has executed at least 11 prisoners – six for collaboration and treason, and five for murder.

The Fatah-dominated Palestinian Authority (PA) in the West Bank also permits capital punishment but has not carried out any executions since 2005. In total, 24 death sentences have been carried out in Gaza and the West Bank since the creation of the PA in 1994.

Human Rights Watch (HRW) said the weekend's executions highlighted the need for a moratorium on death sentences in Gaza. The practice was "cruel and inhuman punishment [and] the persistence of unfair trials made the executions particularly egregious," it said.

HRW said it had documented cases where military courts failed to examine evidence pointing to confessions coerced under torture as well as other violations of detainees' rights. The Independent Commission for Human Rights in Gaza had documented 22 allegations of torture in custody in February alone, HRW said.

The executions were also condemned by the Gaza-based Palestinian Centre for Human Rights. It said the death sentences had been carried out without being ratified by the Palestinian president, Mahmoud Abbas, which violated the constitution.

The death sentence was a "grave and unjustified violation of the right to life and a form of torture and cruel and inhumane treatment", it said.

Amnesty condemned the three executions, saying it was particularly concerned that the men "were executed after sentences issued and ratified by military and criminal courts in Gaza which fail to meet international fair trial standards". It appealed for all pending death sentences to be commuted.

The law permitting the death sentence in Gaza dates back to 1936, when Palestine was under British Mandate rule. It prescribed the method of execution as hanging. The 1970 Palestine Liberation Organisation Rrevolutionary penal code allows the death sentence to be imposed for 42 offences.